In recent years, in order to manage finishing of a surface color of an object, a spectrocolorimetric device for measuring a spectral reflectance on a surface of the object is used (for example, Patent Literatures 1 to 3, or the like). In the spectrocolorimetric device, for example, by using measurement values relating to black chromacity and white chromacity obtained by measurement of two standard colors of black and white, a measurement value relating to the spectral reflectance of the object can be calibrated (for example, Patent Literature 1, or the like).
With respect to such spectrocolorimetric devices, for example, a plurality of spectrocolorimetric devices are used in parallel in a factory or the like, and some of the spectrocolorimetric devices are replaced with new spectrocolorimetric devices, so that a usage situation in which plural types of the spectrocolorimetric devices can coexist can be assumed. As a mode of replacing the spectrocolorimetric devices, for example, there is a mode in which a spectrocolorimetric device that has been used up to now is replaced with a succeeding model of the spectrocolorimetric device.
In this usage situation, if measurement values of two standard colors of black and white are used and the measurement values relating to the object are calibrated, with respect to objects close to black and white, even though the same object is measured by different spectrocolorimetric devices, similar spectral reflectances can be obtained. On the other hand, since calibration methods relating to the optical system and spectral sensitivity are different between different models or between devices manufactured by different manufacturers, if objects of colors different from black and white are measured by different spectrocolorimetric devices, different spectral reflectances can be acquired for different spectrocolorimetric devices.
Therefore, a method of converting a spectral reflectance Rm(i) obtained by measurement of a certain object with a spectrocolorimetric device m to a spectral reflectance Rt(i) obtained by measurement of the same object with another spectrocolorimetric device t by Mathematical Formula (1) is proposed (for example, Non Patent Literature 1 or the like). In Mathematical Formula (1), λ denotes a wavelength, and A(i), B(i), C(i), D(i), and E(i) denote coefficients of the first to fifth terms of the right hand side with respect to each i-th wavelength λ.
                                              ⁢                  [                      Mathematical            ⁢                                                  ⁢            Formula            ⁢                                                  ⁢            1                    ]                                                                                          R            t                    ⁡                      (            i            )                          =                              A            ⁡                          (              i              )                                +                                    B              ⁡                              (                i                )                                      ·                                          R                m                            ⁡                              (                i                )                                              +                                    C              ⁡                              (                i                )                                      ·                                                            dR                  m                                ⁡                                  (                  i                  )                                                            d                ⁢                                                                  ⁢                λ                                              +                                    D              ⁡                              (                i                )                                      ·                                                            d                  2                                ⁢                                                      R                    m                                    ⁡                                      (                    i                    )                                                                              d                ⁢                                                                  ⁢                                  λ                  2                                                              +                                    E              ⁡                              (                i                )                                      ·                                          R                m                            ⁡                              (                i                )                                      ·                          (                              100                -                                                      R                    m                                    ⁡                                      (                    i                    )                                                              )                                                          (        1        )            
In this method, the spectral reflectances acquired by actually measuring a plurality of calibration samples with the spectrocolorimetric device m and the spectrocolorimetric device t are applied to Mathematical Formula (1), so that the coefficients A(i), B(i), C(i), D(i), and E(i) of Mathematical Formula (1) are obtained. By using Mathematical Formula (1) to which the obtained coefficients A(i), B(i), C(i), D(i), and E(i) are applied, the spectral reflectance Rt(i) which is to be acquired by measurement using the spectrocolorimetric device t can be calculated from the spectral reflectance Rm(i) which can be acquired by measurement for any object using the spectrocolorimetric device m.